Optical sheet and lcd apparatus having the same

Abstract

Disclosed are an optical sheet and a LCD apparatus having the same. The optical sheet receives a light emitted from a light guiding plate which is disposed under the optical sheet and emits the light substantially perpendicular to a liquid crystal panel. The optical sheet comprises a first prism pattern made of a material having a first refractive index and a second prism pattern made of a material having a second refractive index which is larger than the first refractive index. The viewing angle of the LCD apparatus having the optical sheet is extended and the brightness thereof is enhanced while a gray scale inversion is reduced.

1 . An optical sheet comprising:
 a first prism pattern having a first refractive index; and   a second prism pattern having a second refractive index larger than the first refractive index,   wherein the first prism pattern and the second prism pattern extend in the same direction, and the first prism pattern overlaps the second prism pattern.   
   
   
       2 . The optical sheet of  claim 1 , wherein the difference between the first refractive index and the second refractive index is greater than or equal to about 0.15. 
   
   
       3 . The optical sheet of  claim 1 , wherein a vertex angle of the first prism pattern is larger than a vertex angle of the second prism pattern. 
   
   
       4 . The optical sheet of  claim 3 , wherein the vertex angle of the first prism pattern is an obtuse angle. 
   
   
       5 . The optical sheet of  claim 3 , wherein opposite sides of a vertex of the second prism pattern have a different slope from each other. 
   
   
       6 . The optical sheet of  claim 5 , wherein one of the opposite sides of the vertex of the second prism pattern comprises a curved line. 
   
   
       7 . The optical sheet of  claim 5 , wherein opposite sides of a vertex of the first prism pattern have a different slope from each other. 
   
   
       8 . The optical sheet of  claim 1 , wherein the first prism pattern has a first pattern pitch p 1  and the second prism pattern has a second pattern pitch p 2 ,
 wherein, |p 1 −N·p 2 |<p 2 /3 and N is a natural number less than 5.   
   
   
       9 . The optical sheet of  claim 8 , wherein the first pattern pitch p 1  is equal to the second pattern pitch p 2 . 
   
   
       10 . The optical sheet of  claim 8 , wherein a vertex of the second prism pattern is disposed apart from a valley of the first prism pattern by a gap g,
 wherein, g≦p 2 /2.   
   
   
       11 . A display apparatus comprising:
 a liquid crystal panel;   a light source generating light used to display an image;   a light guiding plate positioned to receive the light from the light source and emit the light toward the liquid crystal panel; and   an optical sheet disposed between the light guiding plate and the liquid crystal panel, the optical sheet comprising;   a first prism pattern having a first refractive index; and   a second prism pattern having a second refractive index larger than the first refractive index,   wherein, the first prism pattern and the second prism pattern extend in the same direction, and the first prism pattern overlaps the second prism pattern.   
   
   
       12 . The display apparatus of  claim 11 , wherein the difference between the first refractive index and the second refractive index is greater than or equal to about 0.15. 
   
   
       13 . The display apparatus of  claim 11 , wherein a vertex angle of the first prism pattern is an obtuse angle and larger than a vertex angle of the second prism pattern. 
   
   
       14 . The display apparatus of  claim 13 , wherein a cross section of the second prism pattern includes a plurality of scalene triangle shapes. 
   
   
       15 . The display apparatus of  claim 14 , wherein one of the opposite sides of a vertex of the second prism pattern comprises a curved line. 
   
   
       16 . The display apparatus of  claim 14 , wherein opposite sides of a vertex of the first prism pattern have a different slope from each other. 
   
   
       17 . The display apparatus of  claim 11 , the first prism pattern has a first pattern pitch pI and the second prism pattern has a second pattern pitch p 2 ,
 wherein, |p 1 −N·p 2 |<p 2 /3 and N is a natural number less than 5.   
   
   
       18 . The display apparatus of  claim 17 , wherein the first pattern pitch p 1  is equal to the second pattern pitch p 2 . 
   
   
       19 . The display apparatus of  claim 11 , wherein light emitted from the optical sheet is incident substantially perpendicular to the liquid crystal panel and a diffusive member is disposed on the liquid crystal panel to scatter the light in multiple directions. 
   
   
       20 . The display apparatus of  claim 11 , wherein the light source includes a light emitting diode or a lamp and is installed at one or more side edges of the light guiding plate.